Police believe the pills included a quantity of DNP, which is also used as a raw material for explosives.

The orange notice issued by Interpol said: “Although usually sold in yellow powder or capsule form, DNP is also available as a cream.

“Besides the intrinsic dangers of DNP, the risks associated with its use are magnified by illegal manufacturing conditions.

“In addition to being produced in clandestine laboratories with no hygiene regulations, without specialist manufacturing knowledge the producers also expose consumers to an increased chance of overdose.”

The alert comes after the World Anti-Doping Agency (WADA) analysed a sample seized in Australia, prompting fears it has become widely available on the black market.

WADA director general, David Howman said it is “crucial” that DNP does not “reach the hands of athletes”.

He said: “We are appreciative that Interpol has issued this global warning on DNP.

“This is a perfect example of how crucial it is that law enforcement and anti-doping organisations continue to forge closer ties so that dangerous, and potentially fatal, substances such as DNP do not reach the hands of athletes.”

Following Miss Parry’s tragic death West Mercia Police also issued a warning to others of the dangers of buying substances online.

Chief Inspector Jennifer Mattinson said: “We are undoubtedly concerned over the origin and sale of these pills and are working with partner agencies to establish where they were bought from and how they were advertised.

“The coroner’s report will establish the exact cause of Eloise’s death but we urge the public to be incredibly careful when purchasing medicine or supplements over the internet.

“Substances from unregistered websites could put your health at risk as they could be extremely harmful, out-of-date or fake.”